2-chloroprocaine has enjoyed wide clinical usage for a variety of nerve block procedures because it has a rapid onset, short duration, and is quickly hydrolyzed by pseudocholinesterase circulating in the bloodstream. This, plus the fact that the fetus itself has the capability of rapidly hydrolyzing this drug, has made it particularly attractive for use in epidural anesthesia for obstetrics. Recent clinical reports, however, have suggested that under certain circumstances this drug may be neurotoxic to the parturient even in routine clinical concentrations. Attempts to study this potential toxicity in a variety of animal models have led to conflicting and controversial results. This study will directly observe the effect of 2-chloroprocaine and other local anesthetics on endoneurial fluid pressure, peripheral nerve ultrastructure, and nerve blood flow. Other substances known to produce peripheral neuropathies have been studied with these techniques and have shown the development of endoneurial edema with significantly elevated endoneurial fluid pressures. These changes were directly correlated with alterations in peripheral nerve ultrastructure. A decrease in nerve blood flow is a consequence of the elevated tissue pressure in the nerve. The animal model to be used will be the adult Sprague-Dawley rat which has had its sciatic nerve exposed on each side. One side will be injected with a 10 Mul volume of the test local anesthetic solution, while the other side will be bathed in the same solution. Endoneurial fluid pressure will be measured at various times from one hour through thirty days by utilizing a servo-null micropipette system, which is associated with minimal trauma. Morphometry will be studied fom electron micrographs of peripheral nerve to determine the distribution of nerve fibre diameters in control animals and in the animal preparations which have been exposed to the local anesthetics. Should the infusion or perfusion of the local anesthetic solution cause significant rises in endoneurial fluid pressure and/or pathologic changes, nerve blood flow will be measured utilizing techniques already developed in this laboratory.